The invention relates to a device for floating clamping of a workpiece to be machined. The device has a pair of clamping pistons and a pair of clamping jaws which are capable of being advanced onto mutually opposite sides of the workpiece with the aid of the two clamping pistons so as to exert a clamping force acting on the workpiece.
A device of this type is commercially available and may be obtained, for example, under the type designation B1.893 from Rxc3x6mheld, D-35321 Laubauch, Germany. A first clamping cylinder of the known device is formed of a cylinder housing capable of being attached at a fixed location to a base, such as, for example, a machine table or a base plate of a clamping device, and a first supporting piston which is guided in the cylinder housing. The first support piston which, at a supporting-piston end projects out of the cylinder housing, carries a first clamping jaw connected fixedly to the supporting piston and projecting laterally relative to a longitudinal axis of the first supporting piston. The supporting piston forms, in turn, a cylinder housing, in which is guided coaxially to the first supporting piston a second supporting piston which, at an end of the second supporting piston protecting beyond the first supporting piston at the supporting-piston end of the latter carrying the first clamping jaw, carries a second clamping jaw connected fixedly to the second supporting piston and likewise projecting laterally. The second supporting piston has formed on it a piston annular surface facing the second clamping jaw carried by the second supporting piston. The piston annular surface has located opposite it a corresponding inner annular surface formed on the first supporting piston. The first clamping cylinder is configured to be double-acting, in such a way that the first supporting piston, when loaded by a pressurized hydraulic fluid via a first connection of the cylinder housing, assumes, by overcoming a counter-force applied by a spring configuration, an initial position in which the supporting piston is retracted into the cylinder housing. When there is a reduction in pressure at the first connection and loading via a second connection, the first supporting piston is capable, with the assistance of the counter-force of the spring configuration, of being moved into a position which is fixed by a stop and in which the supporting piston is extended out of the cylinder housing. At the same time, hydraulic fluid introduced via the second connection passes into an annular space formed between the annular surfaces explained further above (the piston annular surface on the second supporting piston and the inner annular surface on the first supporting piston), and, after a reduction in pressure has taken place at the first connection and therefore also in the cylinder housing formed by the first supporting piston, causes the second supporting piston to be retracted into the cylinder housing formed by the first supporting piston, so that, when the device is loaded with the hydraulic fluid via the second connection, the two clamping jaws move toward one another and, assuming an appropriate configuration and adaption of the geometry of the device, are capable of being advanced onto mutually opposite sides of the workpiece already clamped in a statically defined manner, under a clamping force acting on the workpiece.
By the device being loaded by the hydraulic fluid via a third connection, the first supporting piston can be detained in a position assumed by the latter, in such a way that the supporting piston can be loaded without any reaction on the hydraulic fluid. For this purpose, the cylinder housing guiding the first supporting piston is provided with an annular chamber communicating with the third connection and has an inner wall which guides the first supporting piston and which is capable, under the pressure of the hydraulic fluid, of being pressed onto the outer surface of the first supporting piston, so that the first supporting piston can be detained frictionally. By contrast, a load exerted on the second supporting piston and acting counter to the clamping force when a workpiece clamped by use of the device is machined on both sides reacts directly on the hydraulic fluid and may cause the second clamping jaw to yield.
In order to avoid inadmissibly high tilting moments on the supporting pistons, the laterally projecting clamping jaws are relatively short, so that the device has to be placed very close to a workpiece to be clamped by it. The geometry of the workpieces to be clamped therefore places narrow limits on the use of the device.
Moreover, the frictional forces caused by the tilting moments and occurring, in particular, between the two supporting pistons make it necessary to use a relatively high pressure of the hydraulic fluid in order to generate the necessary clamping force.
Although the known device makes it possible to reduce its clamping range by a corresponding adjustment of setscrews provided in the clamping jaws, an increase in the clamping range necessitates a lengthening of the second supporting piston and an accompanying greater dimensioning of the device as a whole, since a lengthened second supporting piston must also have increased bending resistance. A given device of the known type, to that extent, also cannot be converted to greater clamping widths.
It is accordingly an object of the invention to provide a device for the floating clamping of a workpiece to be machined which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which is configured in such a way as to obtain as wide a field of use as possible for it.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for floating clamping a workpiece to be machined, including:
two clamping pistons; and
a fixedly articulated collet chuck actuated by the two clamping pistons, the collet chuk having a pair of clamping levers with two clamping jaws capable of being advanced onto mutually opposite sides of the workpiece with an aid of the two clamping pistons so as to exert a clamping force acting on the workpiece, and the pair of clamping levers and two clamping jaws defining a chuk opening.
To achieve the object, the device initially mentioned is developed to the effect that it is equipped with the collet chuck formed from the pair of clamping levers and the clamping jaws and defining a chuk opening, and a fixed articulation of the collet chuck is provided.
A device configured in this way ensures a relatively large free space for placing it in relation to the workpiece to be clamped and, for that reason, provides a relatively wide field of use. Furthermore, this can be widened, with the effect of increasing the clamping range, at relatively low outlay in order to convert a given device, in that, in a preferred embodiment, the collet chuck is merely replaced by one having a chuck opening of increased bit width. In this case, advantageously, the clamping pistons remain completely unaffected by the conversion.
In another preferred embodiment, at least one of the two clamping levers is composed of a fixedly articulatable first arm and of a second arm connectable to the first arm so as to have a variable width of the chuck opening. This entails a particularly low outlay in varying the clamping range of the device.
Advantageously, each of the two clamping pistons is capable of being detained under the action of a pressurized fluid and, after detention has taken place, of being loaded without any reaction on the fluid. In this preferred embodiment, it is unimportant on which of the two clamping jaws is absorbed a supporting force arising from a machining of the workpiece clamped between them, since neither of the clamping jaws can yield as a result of a reaction on the fluid.
In an advantageous development, after the advance of the clamping jaws onto the workpiece has taken place and before the clamping pistons have been detained, the collet chuck can be adjusted in terms of its pivoting position relative to the fixed articulation. There is therefore the possibility of correcting a variation in position of the workpiece which may have occurred during the advance of the clamping jaws onto the latter.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for the floating clamping of a workpiece to be machined, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.